Tuning of the Relative Phases of a Rotary Travelling Wave Oscillator

This letter describes the implementation and performance of a phase detector and algorithm combination used to tune the relative phases of an 18-GHz RTWO. Symmetrical XOR phase detectors are designed (20 GHz simulated operation), fabricated in a SiGe BiCMOS process and tested to resolve approximately 4 mV/° from 35° to 55° and approximately 5 mV/° from 80° to 100° at 12 GHz. Instances of this phase detector are used to measure the phase of nominal 45° differential transmission line sections of an 18-GHz RTWO. The phase alignment algorithm mitigates differences between these measurements by iteratively adjusting varactors placed differentially across the RTWO transmission line sections.